Problem - E - Codeforces

题意：

 

思路：

样例：

 

这种分类讨论的题，主要是去看答案的最终来源是哪几种情况，这几种情况得不重不漏

Code：

#include <bits/stdc++.h>

#define int long long

using i64 = long long;

constexpr int N = 2e5 + 10;
constexpr int mod = 998244353;

int n;
int a[N];

void solve() {
	std::cin >> n;
	for (int i = 1; i <= n; i ++) {
		std::cin >> a[i];
	}

	int ans = 1e9;
	for (int i = 2; i <= n; i ++) {
		int u = a[i - 1], v = a[i];
		if (u > v) std::swap(u, v);
		if (v > 2 * u) {
			ans = std::min(ans, (v + 2 - 1) / 2);
		}else {
			ans = std::min(ans, (u + v + 3 - 1) / 3);
		}
	}

	for (int i = 1; i <= n - 2; i ++) {
		int u = a[i];
		int v = a[i + 2];
		if (u > v) std::swap(u, v);
		if (u % 2 == 1 && v % 2 == 1) {
			ans = std::min(ans, u / 2 + v / 2 + 1);
		}
	}

	std::sort(a + 1, a + 1 + n);
	ans = std::min(ans, (a[1] + 1) / 2 + (a[2] + 1) / 2);

	std::cout << ans << "\n";
}
signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t = 1;

    while (t--) {
        solve();
    }
    
    return 0;
}